This invention relates to contrast agent imaging beam sequences for a medical diagnostic ultrasound system. In particular, transmit and associated receive sequences are provided.
Contrast agents, such as microspheres, are added into a patient to assist in medical diagnostic imaging. Contrast agents are sensitive to acoustic energies. Transmissions of acoustic energy destroy or modify contrast agent. A loss of correlation due to changes of the contrast agent is determined and used to generate a medical diagnostic ultrasound image. In another method of detection, movement of the contrast agent without loss of correlation or in combination with some loss of correlation may be used to generate ultrasound images.
To determine the loss of correlation or movement of contrast agent, multiple beams of acoustic energy along the same lines or to the same locations are transmitted. Resulting echoes from the transmissions are sampled for determining the loss of correlation.
Various transmit and associated energy sequences for loss of correlation or motion detection imaging have been used. For example, a flow sample interleave ratio (FSIR) of one and a flow sample count (FSC) of three are used. As a result, three transmissions for three pulse repetition intervals are fired along each scan line before firing along the next or adjacent line. For each scan line except the edge scan lines for a region of an image, a pulse or energy sequence of e e e C C C e e e is provided, where e represents energy from a transmit pulse along a different scan line (e.g., such as an adjacent scan line) and C represents energy from the transmit pulse along the transmit line of interest. Energy from transmit pulses along adjacent scan lines acts to destroy the contrast agent before the transmissions used for detecting movement or loss of correlation sampling are fired.
Other sampling sequences have been used for motion detection or loss of correlation imaging. For example, a FSIR of two with a FSC of three provides pulse or energy sequences that alternate or differ across alternative scan lines. FIG. 5E represents this example. Imaging pulses are labeled “C” and are associated with displayed scan lines 1 through 5. Collateral energy pulses on one scan line that are from transmissions on neighboring scan lines are labeled “e”. For odd scan lines and ignoring the first scan line in an image, scan line one, the energy sequence comprises e e e CeCeCe, and for even scan lines the energy sequence comprises eCeCeC e e e. For odd number scan lines, a greater amount of bubble destruction before detection sampling is provided than for even scan lines. A FSIR of three with a FSC of three also results in differing energy sequencing as a function of scan line. The different amount of collateral destruction for different scan lines may cause a loss in sensitivity and visual artifacts. While the FSIR=1 sequence minimizes artifacts, poor sensitivity is provided due to the amount of destruction before the imaging pulses.
In another contrast agent imaging technique, one or more transmit pulses designed for destroying contrast agents without associated receive sampling are transmitted. For example, a FSIR=1 with a FSC=3 is used such that a destruction pulse is transmitted between the first two imaging pulses of the flow sample count. Substantially each transmit line is associated with an energy sequence of ede e CDC C ede e, where d is the collateral energy from destruction transmission along adjacent scan lines and D is the destruction transmit pulse along the scan line of interest. Like the other examples above, poor sensitivity is provided due to the amount of destruction prior to an imaging transmit pulse.